System and method of charge management

Abstract

A heat exchanger has an upper region, a lower region disposed vertically lower than the upper region, and a passive charge management device. The passive charge management device has an internal volume, an upper tube connecting the internal volume to at least one of the upper region and the lower region at a first vertical height, and a lower tube connecting the internal volume to at least one of the upper region and the lower region at a second vertical height that is vertically lower than the first vertical height.

What is claimed is: 
     
       1. A heat exchanger, comprising:
 an undivided header; 
 a divided header that comprises a divider that defines a division between an upper region comprising a plurality of supply heat exchanger tubes configured to carry refrigerant into the undivided header and a lower region comprising a plurality of return heat exchanger tubes configured to carry refrigerant from the undivided header, wherein the lower region is disposed vertically lower than the upper region; and 
 a passive charge management device associated with and mounted to the undivided header and comprising:
 an internal volume; 
 an upper tube connecting the internal volume in direct fluid communication with the undivided header at a first vertical height; and 
 a lower tube connecting the internal volume in direct fluid communication with the undivided header at a second vertical height that is vertically lower than the first vertical height; 
 wherein a majority of the internal volume is located adjacent to and vertically below a vertical height of the divider defining the division between the upper region and the lower region. 
 
 
     
     
       2. The heat exchanger of  claim 1 , wherein the plurality of the supply heat exchanger tubes and the plurality of return heat exchanger tubes comprise microchannel tubes extending through the upper region and the lower region, respectively. 
     
     
       3. The heat exchanger of  claim 1 , wherein the first vertical height is at least partially vertically aligned with the upper region. 
     
     
       4. The heat exchanger of  claim 1 , wherein the second vertical height is at least partially vertically aligned with the lower region. 
     
     
       5. The heat exchanger of  claim 1 , wherein the passive charge management device comprises a reservoir that provides a majority of the internal volume of the passive charge management device and wherein the upper tube and the lower tube are in fluid communication with the reservoir. 
     
     
       6. The heat exchanger of  claim 1 , wherein the passive charge management device comprises a reservoir that is vertically aligned with a portion of each of the upper region and the lower region. 
     
     
       7. A method of refrigerant charge management, comprising:
 providing a microchannel heat exchanger comprising an undivided header and a divided header having a divider that defines a division between an upper region comprising a plurality of supply microchannel tubes configured to carry refrigerant into the undivided header and a lower region comprising a plurality of return microchannel tubes configured to carry refrigerant from the undivided header; 
 introducing liquid phase refrigerant into the microchannel heat exchanger; 
 filling the microchannel heat exchanger with refrigerant to a threshold vertical height; 
 continuously introducing liquid phase refrigerant into the microchannel heat exchanger to exceed the threshold vertical height and to receive liquid phase refrigerant into an internal volume of a passive charge management device that is mounted to and in fluid communication with the undivided header, wherein a majority of the internal volume is located vertically below a vertical height of the divider of the divided header; and 
 reducing a compressor discharge pressure in response to receiving the liquid phase refrigerant into the passive charge management device. 
 
     
     
       8. The method of  claim 7 , further comprising:
 reducing a subcooling temperature in response to receiving the liquid phase refrigerant into the passive charge management device. 
 
     
     
       9. The method of  claim 7 , further comprising:
 reducing a rate of increase of subcooling temperature versus an increasing ambient outdoor temperature in response to receiving the liquid phase refrigerant into the passive charge management device. 
 
     
     
       10. The method of  claim 7 , further comprising:
 reducing a rate of increase of compressor discharge pressure versus an increasing ambient outdoor temperature in response to receiving the liquid phase refrigerant into the passive charge management device. 
 
     
     
       11. The method of  claim 7 , wherein the passive charge management device comprises an internal volume and wherein a majority of the internal volume is vertically located between an upper portion of a lower region of the heat exchanger and a lower portion of an upper region of the heat exchanger. 
     
     
       12. An HVAC system, comprising:
 a condenser heat exchanger comprising an undivided header, and a divided header comprising a divider that defines a division between an upper region comprising a plurality of supply heat exchanger tubes configured to carry refrigerant into the undivided header and a lower region comprising a plurality of return heat exchanger tubes configured to carry refrigerant from the undivided header; 
 a compressor configured to pump refrigerant to the condenser heat exchanger; and 
 a passive charge management device comprising an internal volume mounted to and in fluid communication with the undivided header of the condenser heat exchanger, wherein the passive charge management device is configured to receive liquid phase refrigerant into the internal volume from the undivided header of the condenser heat exchanger when a vertical height of liquid refrigerant within the undivided header of the condenser heat exchanger exceeds a threshold vertical height, and wherein a majority of the internal volume of the passive charge management device is located vertically below a vertical height of the divider defining the division between the plurality of supply heat exchanger tubes of the upper region and the plurality of return heat exchanger tubes of the lower region. 
 
     
     
       13. The HVAC system of  12 , wherein the threshold vertical height is vertically aligned with a lower region of the condenser heat exchanger. 
     
     
       14. The HVAC system of  claim 12 , wherein the threshold vertical height is vertically aligned with an upper region of the condenser heat exchanger. 
     
     
       15. The HVAC system of  claim 12 , wherein the passive charge management device comprises an elongated tube reservoir vertically located substantially between a lower region of the condenser heat exchanger an upper region of the condenser heat exchanger. 
     
     
       16. The HVAC system of  claim 12 , wherein the HVAC system is a heat pump HVAC system. 
     
     
       17. The HVAC system of  claim 12 , wherein the plurality of supply heat exchanger tubes and plurality of return heat exchanger tubes comprise microchannel tubes.